The present invention relates to the field of magnetic read and write heads used for tape and disk applications.
Magnetic heads used in magnetic tape applications generally consist of one or more thin film magnetic transducers fabricated on a substrate and mounted with a closure. In the transducer fabrication process, a thick overcoat layer of alumina is deposited between the magnetic transducers and the top closure. The thin film magnetic transducers include read transducers and write transducers. Read transducers typically have a magnetoresistive film, giant magnetoresistive film, or an inductive element for sensing data written in magnetic media. Write transducers are always inductive in nature for writing on the magnetic media. Multiple magnetic heads are often bound together to provide simultaneous read and write capabilities in tape drive applications.
The magnetic tape media is biased against the face of the magnetic head or heads as the media is moved longitudinally relative to the magnetic heads. Rubbing between the tape media and the magnetic heads causes both items to wear. The substrates and closures of the magnetic heads are fabricated from hard materials to help minimize their wear. The magnetic transducers and overcoat layers, on the other hand, are fabricated from materials selected primarily for their magnetic and electrical properties. (Magnetic transducer wear is not a major problem in hard disk applications because the magnetic transducers fly above the hard disk surface on a very thin layer of air.)
The difference in hardness between the substrate and closure, on the one hand, and the magnetic transducer materials and overcoat layer materials, on the other hand, results in uneven wear at the face of the magnetic head due to contact with the magnetic tape media. Since the magnetic transducer materials and overcoat layer materials are softer than the substrate and closure materials, the magnetic transducers and overcoat layers recess quicker from the media-head interface than do the substrate and closure. As a result, a concave shaped gap develops over time between the magnetic transducer and the magnetic tape media. This gap causes poor read and write performance, and even total failure of the magnetic heads in severe recession cases.
Historical attempts to minimize wear of the magnetic transducer materials have involved the utilization of harder materials in the various layers that make up the magnetic transducer. For example, cobalt-zirconium-tantalum alloys and iron-aluminum-nitrogen alloys have been used in place of the softer nickle iron alloys as the magnetic shields and poles in magnetic read transducers and magnetic write transducers respectively. In another example, alumina has been used in place of the softer silicon dioxide as a nonmagnetic bulk insulating material and write gap layer material. However, the selection of harder materials for wear resistance usually remains a secondary consideration behind the magnetic and electrical properties that determine the data recording density. What is desired is a new approach that improves the erosion characteristics of the magnetic heads without adding considerable complexity to the magnetic head fabrication process or requiring a tradeoff of the magnetic read and write performances.
The present invention is an improved method of fabricating magnetic heads and the resulting magnetic head structures. The improvement is the addition of one or more protective layers exposed edgewise at the media-head interface. Each protective layer is situated inside, adjoining or adjacent the magnetic transducers disposed within a magnetic head. Each protective layer is formed from a metal that is harder than the neighboring magnetic layers and insulating layers. The hard protective layer slows the rate at which the magnetic transducers erode and thus prolongs the life of the magnetic head.
Each protective layer added to the magnetic heads adds one extra deposition step to the fabrication process. The protective layers are deposited to a thickness ranging from greater than 0.2 micrometers to approximately 0.5 micrometers each. Thinner protective layers tend to offer insufficient resistance to erosion. Thicker protective layers provide only marginally better performance. Protective layer metals are selected based upon their hardness, ease of use during fabrication, and compatibility with adjoining materials. The protective layers require a hardness of greater than 850 Knoop to be harder than sputtered alumina, the current industrial standard. The metals include, but are not limited to, chromium, iridium, rhodium, tantalum, titanium and tungsten. Each protective layer may be patterned after deposition, as necessary, to open vias and to provide electrical isolation from other conductive layers.
Accordingly, it is an object of the present invention to provide an improved magnetic head having enhanced recession resistance characteristic. The improved may be applied to read-only, write-only, and combination read-write magnetic head configurations.
Another object of the present invention is to provide an improved method for fabricating the magnetic heads to provide the enhanced recession resistance characteristic.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.